1. Field of the Invention
The present invention relates to a core shaft mechanism capable of supporting a hollow core on a winder shaft on which rolls of web material such as paper may be wound.
2. The Prior Art
In winding rolls of sheet of web material, such as a continuous supply of paper in a papermaking machine, it is common practice to provide a hollow tubular cylindrical core on which the paper is wound. The core requires a shaft rotatably supported at its ends to support the core during winding or unwinding operations. A core shaft clamp mechanism is necessary to grip the core in a fixed, coaxial position on the shaft and permit braking or driving of the shaft and the roll supported on the core. The clamp mechanism must also be capable of releasing its grip on the core in order to allow the core to be removed from the shaft.
Previous clamp mechanism for holding the cores on the shafts have involved heavy nuts for tightening U-shaped collars against spacer sleeves which in turn hold the core in place against a fixed flange at the opposite end of the shaft. To remove a core, the nut has to be rotated back on its threads one half inch or more until the U-shaped collar can be withdrawn from about the shaft. A fresh core is placed on the shaft followed by the spacer sleeve. The U-collar is then put in place and the nut tightened. A significant drawback with this construction is that, if cores shrink or compress, the nut can loosen, whereupon the U-collar can then be thrown radially by the rotating shaft imperiling nearby workers and machinery. Compression or shrinkage of cores may be expected particularly when paper, notably tissue paper, is being wound on fiber cores.
Another known core clamping arrangement utilizes a flexible diaphragm for radially expanding the outer diameter of the core shaft into a frictional hold engagement with the core. This construction, however, is very expensive, requiring for example the provision of air connections, and may unduly prolong the operation of mounting the core on the shaft. This mechanism is often difficult to balance the high speed operation and does not maintain reliable concentricity at higher speeds, such that undesirable variation in winding and unwinding tensions results.
The present invention avoids the drawbacks of the prior art by affording a core shaft mechanism that automatically adjusts for a continued gripping force against a core which shrinks or compresses axially during winding operation and which is relatively inexpensive to manufacture and assemble.